This invention relates to a new process for the production of copolyester resin. The invention further relates to a process whereby one produces a copolyester with improved randomization.
There are presently two process routes utilized in the production of copolyester resins. The first is classified as the direct esterification (TPA) process. This process allows a copolyester to be produced when glycols are selected that do not dehydrate under acid conditions. As known to those skilled in the art, the polyester is generally made in two stages. In the first stage or esterification stage, the diacid is reacted with the diol at elevated temperatures and pressures with water being produced. In the second stage or the polycondensation stage, a vacuum is gradually applied, generally a catalyst is utilized, and water and excess diol are withdrawn as a condensation product. The second process is classified as the ester interchange (DMT) process. This process allows a copolyester to be produced when glycols are selected that do dehydrate under acid conditions. As known to those skilled in the art, the polyester is made in two stages. In the first stage or transesterification stage, a dimethyl ester is reacted with a diol at elevated temperatures with an alcohol being produced. In the second stage or polycondensation stage, a vacuum is gradually applied, generally a catalyst is utilized and excess diols are withdrawn as a condensation product.